Electric fences are used in agricultural and pastoral applications, for containing stock within a defined area, or to deter them from entering an area of crops or similar, and also in agricultural and industrial security fencing of installations such as for example power stations, prisons, and similar. An electric fence system comprises an energiser which is typically connected to mains power at a base station but may be battery powered, and which is connected to a fence line and emits a high voltage pulse approximately every second to the fence line. The intensity of the pulse is such that it deters animals and persons from touching the electric fence.
An electric fence may often be many kilometers in length, particularly in agricultural and pastoral applications. At least one system is now available which includes a remote control unit which may be carried by a farmer and which enables the farmer to energise or de-energise the fence from any point on the fence line, by remotely turning the energiser off and on. The remote control unit is applied to the fence line and transmits a coded signal along the fence line to the energiser. NZ patent specification 258240 describes such a system in which the control signal sent from the remote unit to a receiver in the energiser is a coded digital signal.